Carburetor



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1937- A. D. GLADWELL 2,102,362

GARIURETOR Filed Feb. 7, 1936 'LUI. H0 6L L|QU|U CUNTACT APPARATUS.

Patented Dec. 14, 1937 UNITED STATES UVUI VII I IV CARBURETOR ArthurWilliam David Gladwell, London, England Application February 7, 1938,Serial No. 62,853

In Great Britain July 18, 1935 Claims.

This invention relates to carburetors for internal combustion enginesand has for its object to provide improved automatic means for varyingthe choke area so as to afford a varying passage area dependent on thesuction or depression, the variation preferably comprising a slightinitial reduction of the original area for accelerating and a subsequentsteady increase for high speed and maximum power up to the full areaavailable.

According to this invention, the spraying nozzle is mounted within achoke tube having its upper or divergent portion fitted internally withdisplaceable elements adapted to be drawn alon by the air current pastthe nozzle. The displaceable elements may consist for example of metalballs loosely engaged in open-sided cells orfiutings formed along theinterior of the choke tube, the width of the openings at the surface ofthe tube being slightly less than the diameter of the balls.

The invention is hereafter described with reference to the accompanyingdrawing, in which:-

Fig. 1 is apart sectional elevation of the body or mixing chamber of avertical carburetor having a variable choke tube according to theinvention.

Fig. 2 is a plan view of the choke tube.

Fig. 3 illustrates the preferred method of making the choke tube.

Referring to Fig. 1, the carburetor comprises a mixing chamber I0 havingits lower portion H of frusto-conical shape, open to the atmosphere atthe bottom and formed with a cross-bar |2 which supports the sprayingnozzle l3. The upper part [4 of the mixing chamber is of cylindricalshape, provided with means, such as a flange l5, for attachment to thethrottle chamber |6 leading to the engine. Inside the cylindrical upperpart M there is mounted a choke tube I1, resting upon a step |8 in thewall of the chamber, and retained by the flange IQ of the throttlechamber.

The spraying nozzle comprises a cap 2| secured to the top of a centraltube 22 within an outer tube 23, the latter being supported by apolygonal base 24 of which the shank 25 is screwed into a hole 26 in thehollow cross bar l2 extending from one side to the other of the mixingchamber below the choke tube I1; the lower end of the mixing chamber isshown as of greater width, to compensate for the restriction formed bythe cross-bar l2. Gasoline or other fuel is fed from a float chamber(not shown) through a duct 21 in the cross-bar |2 to a central bore 28into which the lower end of the tube 22 is screwed or otherwise securedso as to prevent leakage of fuel at this point. A second duct 29extending in the opposite direction along the cross-bar |2 admits air atatmospheric pressure to the space around the lower end of the fuel tube22, this air being warmed or heated if desired, for example by contactwith the exhaust manifold of the engine; the temperature of the air thusadmitted may be from 35 to 70 C., for example, in the case of gasolineof standard quality.

The cap 2| has a central perforation 30 registering with the bore of thefuel tube 22, the parts being secured together by means of a boss 3| onthe bottom of the cap; this boss is shown as being counterbored,coaxially with the perforation 30, to receive the upper end of the tube22, which is preferably soldered in place. The exterior of the cap 2| isformed with a rounded rim 32 which is shouldered down at 33 so as to fitthe upper end of the outer tube 23, the cap 2| being held down on thelatter by the at tachment of the inner tube 22; the rim 32 produces aslight restriction of the passage through the choke tube II.

The choke tube I! has approximately the usual Venturi-shaped orconvergent-divergent interior, as indicated at 34, but the passage areais controlled by the presence of steel balls 35 loosely engaged inopen-sided cells or flutings 38 formed along the interior. The hallsproject inwardly of the choke tube, for example to the extent ofone-quarter of their diameter, so as to restrict the passage area attheir own level, as compared with the circular or annular area of anormal choke tube of the same diameter. The flutings 36 (see Fig. 2) arepreferably part-circular in cross-section, more than semi-circular inextent, and of radius slightly greater than the balls 35; their opensides, towards the interior of the choke tube, afford gaps 31 slightlynarrower than the diameter of the balls mounted in them. They extendlongitudinally down from the top of the choke tube to the level of thethroat or narrowest portion 38 of the interior, so that in-the normalposition shown in Fig. 1, with the balls resting at the bottom of thecells or flutings 36, the area of the throat is restricted by theinwardly projecting surfaces of the balls; the throat 38 may comprise,as seen in Fig. 1, a short cylindrical portion between theconvergent anddivergent portions of the choke.

The top of the nozzle cap 2| provides a central divergent cavity 39, inthe form of a shallow inverted cone, coaxial with the perforation 30,the walls of this conical cavity being for example at an angle of 30 tothe horizontal so as to form a sharp edge at their junction with the rim32. Oblique holes 40, preferably three or more in number, evenly spacedround the axis, and of a diameter which may be from .030 to .050 inch,for example, are formed in the divergent walls of the cavity 39, theseholes connecting with the top of an annular space or chamber 4| insidethe tube 23 and concentric with the fuel tube 22; these holes 40 mayalso be inclined at an angle of 30 to the horizontal, and they arearranged in radial planes so that their axes and that of the fuel tube22 and perforation 30 intersect at a point 42 within the cone 39.Partitions or baflles, for example of helical form, may be inserted inthe annular chamber 4!, as indicated at 43.

The head of the nozzle I3 extends just above the level of the throat 38,and the circumferential rim 32 of the cap 2| projects about one or twomillimeters radially beyond the outer tube 23; this rim 32 lies at aslightly higher level than the restricted area provided by theprojecting surfaces of the balls 35 in their normal position. When moresuction is applied by the opening of the throttle, the increased flow ofair through the choke tube ll tends to lift the balls 35 inside theircells 36 and carry them along to the upper and wider part of the choketube, thus removing the restriction from the throat and reducing itsproportional effect as the balls rise towards the final position shownin dotted lines at 35a in Fig. 1. But at the initial opening of thethrottle from the idling position, the lifting of the balls firstcarries them to the level of the rim or bead 32 at the head of thenozzle l3, thereby producing a greater restriction, and only thereafterdoes the passage area become increased; the effect of this initialrestriction is to provide a richer mixture at the moment of opening thethrottle for acceleration after a period of slow running, and thus toavoid the fiat spot which is liable to cause engine stoppage under suchconditions.

In operation, the fuel issuing from the perforation 30 will be met bythe oblique streams of air drawn from the holes 40 by the injectoreffect of the engine suction, these streams breaking up the fuel into afine mist (as indicated at 44) which mixes with the main air supplypassing round the exterior of the nozzle l 3; the atomizing air, drawnfrom the duct 29, will have passed through the interior of the base 24into the annular space or chamber 4| between the two tubes 22 and 23, sothat this air (if sufiiciently heated) will have raised the fuel in thetube 22 to a temperature approaching or exceeding its initial boilingpoint, before it issues from the perforation 3U, vaporization thereforetaking place immediately into the main air current.

The number and size of the oblique air holes 40 may be varied; theseholes have a limiting effect upon the quantity of fuel passed at highspeeds, so that the fuel consumption remains approximately proportionalto the power developed. The divergent cavity 39 also acts to some extentas a basin for catching drops of fuel, the sharp edge of the cap abovethe rim 32 preventing the fuel from dribbling down the outside of thenozzle [3 at low speeds.

The cells or fiutings 36 in the choke tube I! can conveniently be formedby drilling evenlyspaced oblique holes 41 into the body of a cylindricalmetal blank 48, as indicated in Fig. 3; this blank is then bored out toform the convergent-divergent interior of the choke tube, as indicatedby the chain-line circles 49-50 representing'respectively the throat 38and the top of the choke tube l1, thereby removing the walls of theholes 41 nearest to the axis for substantially the whole of their axiallength. The choke tube will then appear as shown in Fig. 2, with theopen-sided cells or fiutings 36 each adapted to receive one ball. With achoke-tube having a. 24 millimeter throat and an internal diameter of 28millimeters at the top, there may be employed nine balls each A, inch indiameter, fitted in cells of fiutings formed by drilling holes of inchdiameter at an obliquity of 6%; degrees to the axis, corresponding tothe divergent side of the choke, the pitch circle of the balls varyingby about 3 millimeters in diameter with an axial movement of about inchbetween their extreme positions. When fully raised, the balls will beretained by the connecting flange or facing l9 to which the carburetorbody is secured, so that they cannot slip out of place.

It will be understood that the invention is not limited to the use ofsteel balls as displaceable elements controlling the passage areathrough the choke tube l1, and that it may be applied to carburetors ofother types than that above described, for example to carburetors havingthe axis of the choke tube l1 and spraying nozzle [3 inclined to thevertical; in cases where the axis approaches the horizontal position,the gravity control of the displaceable elements may be supplemented orreplaced by spring or like control. The choke tube may be adapted to anyexisting carburetor having the usual form of choke, the dimensions beingarranged to suit the carburetor to which the choke is to be fitted.

What I claim is:-

1. In a carburetor having a spraying nozzle mounted coaxially within achoke, a choke member having a convergent inlet portion and a divergentoutlet portion, said outlet portion having its inner surface formed withfiutings extending approximately from the throat of said choke member tothe end of said outlet portion, said fiutings being open for theirentire length inwards of said surface, and elements loosely confined insaid fiutings, said elements partly projecting from the open sides ofsaid fiutings to restrict the passage through said outlet portion andbeing controlled by the air current through said choke.

2. In a carburetor having a spraying nozzle mounted coaxially within achoke, a choke member having a convergent inlet portion extending frombelow the outlet of said nozzle and an upper outlet portion extending toabove the outlet of said nozzle, said outlet portion having its innersurface formed with longitudinal fiutings, said fiutings being open fortheir entire length inwards of said surface, and displaceable elementsconfined in said fiutings, said elements partly projecting from the opensides of said fiutings to restrict the passage through said divergentportion and being lifted by the air current through said choke, said aircurrent having free access to the upper faces of said elements throughthe open sides of said fiutings.

3. In a carburetor having a spraying nozzle mounted coaxially within achoke, a choke member having a convergent inlet portion and a divergentoutlet portion, displaceable elements loosely mounted at the innersurface of said di-' vergent portion, said displaceable elements beingadapted to restrict the passage through said di- 7 aus. GHQ QL LEL 'LiU(JUNIAQI APPARATUS.

UUIII UH ii i' vergent portion and having their position controlled bythe air current through said choke, said nozzle extending above saiddispiaceable elements in their normal position, and a peripheralenlargement at the upper end of said nozzle for restricting the passagethrough said choke at a transverse plane of said divergent portioncorresponding to the position of said displaceable elements wheninitially displaced by the air current.

4. In a carburetor having a spraying nozzle mounted'coaxially within achoke, the combination of a nozzle having a peripheral enlargementadjacent to its outlet, a choke member having its throat below the planeof said enlargement, and displaceable elements loosely mounted in saidchoke, said elements partly projecting from the inner surface of saidchoke to restrict the passage therethrough and being controlled inposition by the air current longitudinally of said choke, and

the displacement of said elements with increase of said air currentcarrying them from a position below said enlargement to a position abovesaid enlargement.

5. In a carburetor having a spraying nozzle mounted coaxially within achoke, a choke member having a convergent inlet portion extending frombelow the outlet of said nozzle and an upper outlet portion extending toabove the outlet of said nozzle, said outlet portion having its innersurface formed with open-sided flutings extending to the upper end ofsaid outlet portion, and displaceable balls loosely engaged in saidflutings, the opening along the inner side of each fiuting beingsubstantially parallel and of width slightly less than the diameter ofthe ball engaged in the respective fluting.

ARTHUR WILLIAM DAVID GLADWELL.

